Fire door control apparatus



y 1968 w c. FREDRICK, JR, ET AL 3,383,796

FIRE DOOR CONTROL APPARATUS Filed Nov. 4, 1965 5 Sheets-Sheet 1 May 21, 1968 C. m JR ET AL 3,383,796

FIRE DOOR CONTROL APPARATUS Filed Nov. 4, 1965 5 Sheets-Sheet :2

9 INVENTORS. W

A'ITORN E Y5.

May 21, 1968 Q FREDRHCK, JR" ET AL 3,383,796

FIRE DOOR CONTROL APPARATUS Filed Nov. 4, 1965 5 Sheets-Sheet 3 I 5 2" v gov/M ATTORNE Y5 United States Patent Ohio Filed Nov. 4, 1965, Ser. No. 506,368 4 Claims. (Cl. 49-7) ABSTRACT OF THE DISCLOSURE The application discloses a heat responsive fire door control apparatus for closing a fire door with reference to a door opening. The structure comprises a horizontal trolley rail of inverted U-shape in cross section mounted in a horizontal plane above the door opening and extending transversely beyond one side of the door opening, and a fire door suspended from the rail by means of trolleys tracked within the trolley rail, adapting the door to be translated from an open to a closed position. The door is free to be shifted to open or closed position manually and is closed automatically in the event of a fire by operation of a fire control trolley normally residing within an end portion of the trolley rail in position to engage one of the door support trolleys. For closing the door in response to a fire, a spring-loaded retriever reel is connected by a retriever cable to the fire control trolley for shifting the trolley and the door from the open to the closed position. The fire control trolley normally is disconnected from the door and is latched in a retracted position by a latching mechanism within the rail, which is connected to a heat-responsive fire control cable having one or more fusible links arranged to melt in response to a predetermined increase in temperature as a result of a fire, allowing the latching mechanism to release the fire control trolley, whereby the retriever cable, by operation of the reel, pulls the trolley into engagement with one of the door support trolleys to shift the door to its closed position with reference to the door opening.

One of the primary objectives of the invention has been to provide a simple, heat responsive fire door control apparatus in which the door is slidable and normally resides in an open position, and which shifts to a closed position in response to a predetermined rise of the air temperature in the door area.

According to this aspect of the invention, the fire door is translatably hung from an overhead trolley rail by door support trolleys for horizontal motion. The door normally resides in an open position parallel with the fire wall to one side of the door opening.

The fire door control apparatus essentially comprises a fire control pusher trolley norm-ally residing in an inactive position at the outer end portion of the overhead support rail adjacent the open fire door and adapted to push the fire door automatically to a closed position with reference to the door opening in the event the surrounding air rises to the predetermined temperature. The control apparatus includes a trigger mechanism and a fire control cable normally restraining the fire control trolley, with at least one but preferably two fusible links anchoring the free end or ends of the first control cable to the fire wall. A spring-operated retriever reel includes a retriever cable connected to the fire control trolley, tending to draw the trolley in a door closing direction; however, the trolley is restrained by the trigger mechanism and fire control cable.

In the event of a fire, one or both of the fusible links melt at the predetermined temperature, thus releasing the ice fire control cable and trigger mechanism, whereby the retriever reel is free to draw the fire control trolley into engagement with one of the door support trolleys and thereby to shift the door from its normally open to its closed position.

Another objective of the invention has been to provide a fire control apparatus which permits the fire door to be shifted manually to its opened or closed position without interference from the fire control apparatus and without any restraining action by the retriever mechanism.

According to this aspect of the invention, the overhead door support trolley rail is mounted in a horizontal plane above the door opening and with a substantially equal portion extending beyond the door opening to one side. The door is free to be shifted manually under ordinary usage without being influenced by the fire control apparatus. In other Words, the fire control apparatus normally is disconnected from the door to prevent any inteference with manual opening or closing of the door. In the event of a temperature increase, causing melting of the fusible link, then the fire control apparatus causes the fire control trolley to be shifted by the retriever mechanism into engagement with one of the door support trolleys, thereby to shift the door to its closed position in an automatic manner.

A further objective of the invention has been to provide a fire control apparatus which may be reset in a simple convenient manner after having been tripped by a rise in the air temperature due to fire, with melting of the fusible link or links and automatic closing of the door.

In resetting the door after it has been tripped to its closed position as the result of a fire, the door is simply pushed back manually to its open position, thus forcing the fire control trolley back to the outer end portion of the support rail counter to the pull exerted by the retriever mechanism. Thereafter, replacement fusible links are attached to the end of the fire control cable and anchored to the fire wall. This places the trigger mechanism in engagement with the fire control trolley, thus latching the trolley in its retracted position. The fire door is then free to be operated manually under ordinary usage without any restraining action by the fire control apparatus.

The various features and advantages of the invention will be more clearly apparent to those skilled in the art from the following description taken in conjunction with the drawings.

In the drawings:

FIGURE 1 is a fragmentary elevation illustrating generally the fire door and its control apparatus with refer ence to the door opening in a fire wall.

FIGURE 2 is an enlarged fragmentary view, partially in section, illustrating generally the arrangement of the fusible link, trigger mechanism, supporting trolleys and retriever reel of the invention.

FIGURE 3 is a view taken along the line 3-3 of FIG- URE 2, further detailing the support rail and trolleys of the fire door.

FIGURE 4 is an enlarged fragmentary sectional view similar to FIGURE 2, showing the action of the trolleys and fire door in the event of a fire which raises the temperature sufficiently to melt one or both of the fusible links.

FIGURE 5 is an enlarged sectional view taken along line 55 of FIGURE 4, further illustrating the support rail, one of the door support trolleys, and a portion of the fire door in relation to the door opening.

FEGURE 6 is a fragmentary view similar to FIGURE 1, showing the fire door in its closed position in response to the melting of one of the fusible links.

FIGURE 7 is a sectional view taken along line 7-7 of FIGURE 6, diagrammatically illustrating the binder or stop bracket which engages the leading edge of the fire door in its closed position.

FIGURE 8 is a sectional view, taken along line 88 of FIGURE 6, detailing the stay or guide roller which guides the lower edge of the fire door in its vertical plane during its closing motion with reference to the door openmg.

FIGURE 9 is a general view similar to FIGURE 1, showing a modified arrangement in which two fire doors are utilized in sealing off an opening in the wall which is substantially wider than the opening shown in FIGURE 1.

FIGURE 10 is a fragmentary section showing the double door arrangement in its closed position in response to an elevated temperature resulting from a fire.

FIGURE 11 is a fragmentary view similar to FIGURE 2, illustrating a modified arrangement of the control apparatus in which there is provided a single control cable and fusible link in place of the double link and cable loop arrangement.

Single fire door structure and mounting arrangement As shown generally in FIGURE 1, the single fire door, indicated generally at 1, is mounted with reference to the door opening 2 of a fire wall 3 which rises from a floor 4. The door 1 is suspended by means of a pair of door support trolleys, indicated generally at 55, which traverse an overhead trolley rail, indicated generally at 6. The rail 6 is secured to the wall 3 and extends above the door opening 2 and to the left (in the present example) a suficient distance to suspend the door in its 1 open position parallel with the wall and adjacent the door opening 2. The lower edge of the door 1 is spaced slightly above the floor surface 4, as indicated at 7 (FIGURE 1), and is guided for motion in its horizontal plane parallel with the wall 3 by a guide or stay roller, indicated generally at 8.

Described in detail, (FIGURES 2-5), the trolley rail 6 is generally of inverted U-shape formed of sheet metal and having inturned horizontal flanges 1010 projecting inwardly toward one another from the lower edges of the vertical limbs 11-11 of the rail. The inner or free edges of the horizontal flanges 10 each include a vertical lip 12. The vertical lips 12-12 delineate a central longitudinal slot 13 (FIGURE 5) which provides clearance for the hangers, as described later, which depend from the trolleys 5 and support the door. The support rail 6 is mounted with respect to the wall 3 above the door openings 2 by means of a series of mounting brackets 14 (FIGURES l, 2 and 5), which are of U-shape configuration embracing the support rail 6 and including portions engaging the horizontal flanges 10 of the support rail in load bearing engagement. Each mounting bracket 14 includes an upstanding portion 15 traversed by a bolt 16 passing into the wall 3.

Each door support trolley 5 comprises a carriage 17 (FIGURE 2) supported by rollers 18 which are journalled as at 19 in pairs upon opposite ends of the carriage 17. The rollers 18 track upon the horizontal flanges 10 of the support rail 6, as shown in FIGURE 5. Each carriage, at a point mid-way along its length, includes a trolley hanger 20 (FIGURES 4 and 5) depending downwardly through the slot 13 of the support rail. Each hanger is secured to the carriage by a nut 21, the lower end of the hanger being connected to the upper edge portion of the door as at 22, such that the door is suspended by the pair of trolleys 5-5.

The door 1 is formed of sheet metal of conventional design. Essentially, the door comprises a pair of spaced parallel panels 2323 (FIGURE 5) formed preferably of sheet metal and having marginal U-shaped framing members 24 formed of sheet metal extending along its upper and lower edge portions and also along its opposite side edges. The framing member 24 includes limbs facing inwardly. The upper and lower edge portions and the side portions of the door further include second U- shaped framing member 25 also of U-shaped configura- 4 tion, with the open side of the U facing outwardly. The door panels 23-23 preferably are spot-welded to the framing members 24 and 25 and may include a suitable filler (not shown) between the panels. The respective trolley hangers 20 project downwardly through the slot 13 and are secured as at 22 as noted earlier, to the upwardly facing framing member 25 (FIGURES 4 and 5).

As indicated generally in FIGURE 1 and detailed in FIGURE 8, the guide or stay roller 8 is mounted upon a shaft 27 rising upwardly from an angle bracket 28 which seats upon the floor 4 and is secured as at 39 to the wall 3. The shaft 27 passes through the horizontal portion of the angle bracket 28 and includes a nut 31 which is seated in the floor 4. The roller 8 rides within the downwardly facing U-shaped framing member 25 and thus confines the lower edge of the door in its vertical plane of motion from its open to its closed position (FIGURES 1 and 6).

In its closed position, the leading edge of the door is engaged by a stop element or binder 32 (FIGURES 6 and 7). The binder stops the door preferably before the leading door support trolley 5 strikes the retriever reel assembly, which is indicated generally at 33 in FIG- URES 1 and 6. As detailed in FIGURE 7, the stop element 32 is in the form of a sheet metal bracket secured as at 34 to the wall 3 adjacent the right edge of the door opening 2. The stop element includes an outwardly projecting stop flange 35 which engages the leading edge of the door in its closed position and a flared flange 36 which embraces the leading edge portion to guide and hold the leading edge portion of the door in place with respect to the door opening in its closed position.

It will be understood at this point that the door 1 is free to be opened or closed manually in the usual way without any interference from the fire door control apparatus. For this purpose, the door is provided with a hand grip opening 37 (FIGURE 1) at its leading edge portion for manual operation.

Fire door control apparatus (single door) As best shown in FIGURES l4, the heat responsive control apparatus comprises a retriever reel assembly, indicated generally at 33, connected by a retriever cable 40 to a fire control pusher trolley, indicated generally at 41. The fire control pusher trolley 41 is similar to the door supporting trolleys 5 and normally resides in the left end portion of the trolley rail 6 (FIGURE 2). The pusher trolley is normally restrained in its left hand inactive position by a heat responsive fire control cable loop, indicated at 42.

The retriever reel assembly in general (FIGURES 2 and 3), comprises a housing 43 formed of sheet metal having mounting flanges 44 at opposite ends which are secured by bolts 45 to the fire wall 3. The housing 43 of the retriever reel assembly 33 is mounted adjacent the open right end of the trolley rail 6 (FIGURE 2) and the retriever cable 41? passes from the housing 43 directly into the trolley rail and extends therethrough to the pusher trolley 41, whereby the trolley rail 6 encloses and protects the retriever cable from damage. The retriever reel assembly includes a retriever reel 46 rotatably mounted on a shaft or arbor 47 within th housing 43 (FIGURE 2). The reel includes an internal winding spring (not shown) having one end anchored to the shaft 47 and its opposite end anchored to the reel 46. The spring exerts a constant winding force upon the reel in the direction indicated by the arrow 48 in FIGURES 2 and 3, thus tending to pull the fire control pusher trolley 41 constantly toward the right against the restraining action of the fire control cable 42.

The fire control trolley 41 comprises a carriage 50 (FIGURE 2) having rollers 51 arranged in pairs at opposite ends of the trolley and journalled as at 52 with respect to the carriage. A pusher bar 53 is secured as at 54 to the top of carriage 50. The leading end portion of pusher bar 53, which is formed of sheet metal, is doubled upon itself to provide an abutment '55 and an upstanding flange 56. The retriever cable 40 is anchored as at 57 to the flange 56.

The opposite ends of the fire control cable 42 are anchored as at 58 (FIGURE 2) to respective fusible links 6060 each link having one end anchored to the fire wall 3 as at 61. The opposite or free end of each link includes an aperture 62 to receive the anchored end portion 58 of cable 42. The fusible links 60 are formed of a metal which melts at a temperature somewhere in the neighborhood of 160 F. so as to release one or both ends of the fire control cable loop 42 in response to an elevated temperature resulting from a fire.

The looped lower end of the control cable link 42 passes slidably, as at 63 through the eye 64 of an S-shaped link 65 (FIGURE 4), the link 65 having a second eye 66 pivotally connected to a trigger bar 67 (FIGURE 4). The trigger bar 67 is pivotally mounted as at 68 with reference to the trolley rail 6 and its lower end projects through a catch opening 70 (FIGURE 2) formed in the trailing end portion of the pusher bar 53. The fire control cable loop 42 and trigger bar 67 thus latch pusher bar 53 and fire control cable in the normal left-hand position (FIGURE 2) counter to the pull exerted by the retriever cable 40. It will be seen that under normal conditions, the door 1 is entirely disconnected from the fire control pusher trolley 41 and other components of the control apparatus, leaving the door free to be shifted to its open or closed position manually in the usual way.

Operation In the event of a fire which generates sufficient heat to melt one or both of the fusible links 60 as indicated at 71 (in the present example the upper linkFIGURES 4 and 6), the upper end of control cable 42 is released and drops downwardly. Upon release of the cable 42, the trigger bar 67 is permitted to swing from the latching position of FIGURE 2 to the unlatching position of FIGURE 4. As soon as the trigger bar 67 is thus released, the fire control pusher trolley 41, by operation of the retriever cable 40, is pulled toward the right, causing the abutment 55 of pusher bar 53 to engage the end of the carriage 17 of the left door support trolley 5.

At this point, by operation of the retriever reel 46 and retriever cable- 40, the fire door 1 is shifted toward the right. This motion of the door continues until the leading edge of the door 1 is engaged by the stop element 32, with the door 1 closed with respect to the door opening 2 (FIGURE 6). As noted earlier, the lower portion of the door 1 is guided by the stay roller 8, such that the door is confined in its vertical plane of movement toward the right until it is engaged by the stop element 32 in its closed position.

In resetting the fire door 1 after a fire, the door 1 is pushed back to its open position, thus forcing the fire control trolley 41 back to its left hand position counter to the pull of the retriever assembly 33 (FIGURE 2). A fusible link 60 to replace the melted link 71 is then coupled to the control cable 42 and anchored to the wall so as to reposition the trigger bar 67 to its latching position with respect to the fire control pusher trolley 41. The door 1 may then be closed or opened manually without interference by the fire control apparatus.

Modified structure (double door) The modified structure shown in FIGURES 9 and utilizes the same principles described above, applied to a double door as distinguished from the single door. As shown generally in FIGURE 9, the double doors 7272 are suspended from an overhead trolley rail 73 by door support trolleys 74 tracked in the rail 73. The rail 73 is supported by brackets 75 secured to the fire wall 76 which includes the door opening 77. The lower edges of the doors 72 are guided in their vertical path of motion by the 6' stay rollers 78 in a manner similar to the stay rollers 8, previously described.

In the present arrangement there is provided a pair of retriever reel assemblies indicated generally at 80-80 secured to the fire wall 76 at the center of the door opening 77. The retriever cables 81 of the retriever reel assemblies are each connected to a respective fire control pusher trolley 82 (FIGURE 11) identical to the trolley 41 previously described.

The door control apparatus comprises two control cables 8383 in the form of loops. The inner ends of the loops, at the center of the door opening 77, are joined together by respective fusible links 8484 which are anchored to the fire wall 76. The outer portions of the control cables 83 preferably pass slidably through respective S-shaped links 65 (FIGURE 4), the links 65 being connected to respective trigger bars 86-86 which normally restrain the fire control pusher trolleys 82, as explained earlier in conjunction with the trolley 41.

In case of fire, one or both of the fusible links 8484 will melt at the predetermined temperature, permitting the double doors 72 to be shifted toward one another by their reel assemblies 8080 to the closed position. Thus, if the lower link fails, as indicated at 87 (FIGURE 10) the free ends of the cable will slide with respect to the S-shaped links, releasing the trigger bar 86 and permitting the fire control trolleys 8282 to shift the door 72 to the closed position shown in FIGURE 10. A similar action takes place if the upper fusible link 84 melts, or if both upper and lower links melt under an abnormal temperature.

Single cable fire control apparatus The modified control apparatus disclosed in FIGURE 11 utilizes the same principles as disclosed above except that a single fire control cable is utilized in place of the cable loop. The modified structure utilizes a fire control pusher trolley 41, as previously described with reference to FIGURE 2, having a pusher bar 53 which is connected to the retriever cable 40. The pusher bar 53 is adapted to engage one of the door support trolleys 5 in the event of a fire. The control apparatus includes the same trigger bar 67 pivotally connected as at 68 to the trolley rail 6, with its lower end engaging the catch opening 70 of the pusher bar.

The upper end of the single fire control cable 90 is anchored by means of a fusible link (not shown) to the fire wall in the same manner as the double links 60 shown in FIGURE 2. The lower end of the control cable 90 is anchored as at 91 to a turnbuckle 92 of conventional design to permit tension adjustment of the fire control cable 90. The turnbuckle 92 is connected to a link 93 having one end pivotally connected as at 94 to the trigger bar 67. The fire control cable 90 and trigger bar 67 thus latch fire control trolley 41 in the left-hand position shown in FIGURE 11.

In the event of a fire causing the link to fail, the upper end of the fire control cable 90, which is anchored to the fusible link, is released thus permitting the trigger bar 67 to swing to the release position previously described with reference to FIGURE 4. The retriever cable 40 then pulls the fire control trolley 41 to the right, causing the fire control door to be shifted to its closed position. It will be understood that the single cable can be utilized either in controlling the single door arrangement (FIGURE 1) or the double door arrangement shown in FIGURE 9. In the double door arrangement, two single fire control cables 90 may be joined to a single fusible link as shown in FIGURE 9.

Having described our invention, we claim:

1. A heat responsive fire door control apparatus adapted to close a door with reference to a door opening in a fire wall comprising:

a support rail mounted in a generally horizontal plane,

the support rail having a first portion extending above and across the door opening and having an open end, the support rail having a second portion extendin g transversely beyond one side of the door opening;

said support rail being generally of inverted U-shape in cross section and having inturned flanges projecting toward one another along the lower edge thereof and delineating a longitudinal slot;

a plurality of spaced door support trolleys translatably confined within said support rail and having pairs of rollers tracked upon the inturned flanges of the rail, said trolleys having hangars projecting downwardly through the slot and connected to the door for shiftably suspending the door from the rail for movement to an open or closed position relative to the door opening;

a fire control trolley translatably confined within said support rail and having pairs of rollers tracked upon said inturned flanges, said fire control trolley normally residing in a retracted position at the transversely extended end portion of said rail;

said fire control trolley normally disconnected from the door, adapting the door to be shifted manually to an open or closed position;

a spring-loaded retriever reel secured to the fire wall and including a retriever cable connected to the fire control trolley and normally urging the trolley in a door closing direction;

the said retriever reel including a housing mounted adjacent the open end of the first portion of the support rail which extends above and across the door opening, whereby the retriever cable extends from the housing and through the support .rail to the fire control trolley and being enclosed and protected by the support rail;

a trigger mechanism mounted within the extended end portion of the support rail and including a trigger bar element pivotally connected at a mid-point along its length to the support rail, said trigger bar element having a lower end portion disposed within the rail and normally engaging and latching the fire control trolley in a retracted position, said trigger bar element having an upper end portion projecting upwardly above the rail;

a heat responsive fire control cable having one end anchored to the fire wall and having an opposite end connected to the upper portion of the trigger bar element and normally holding the same in said latching position with respect to the fire control trolley;

said heat responsive fire control cable adapted to part and to release the trigger bar element at a predetermined temperature above normal, whereby said retriever reel is adapted to shift the fire control trolley in a door closing direction in the event of a fire;

said fire control trolley, upon release thereof, adapted to engage one of the door support trolleys, thereby to shift the door to its closed position by operation of retriever reel.

2. A heat responsive fire control apparatus as set forth in claim 1 in which the heat responsive fire control cable includes a fusible link interposed therein, said cable having one end portion anchored to the fire wall, the opposite end portion of the fire control cable being connected to the trigger bar element and holding the trigger bar element normally in a latching position counter to the force exerted by the retriever cable and reel, thereby latching the fire control trolley in said retracted position relative to the fire door, said fusible link adapted to melt at a pretermined temperature, thereby to part the fire control cable and adapting the trigger bar element to be swung about its pivot point to a release position, thereby causing the fire control trolley to be drawn by the retriever cable into engagement with the door to shift the door to a closed position with reference to the door opening of the fire wall.

3. A heat responsive fire door control apparatus as set forth in claim 1 in which the fire control trolley includes a pusher bar disposed within the support rail and having a catch opening and in which the trigger mechanism incuudes a trigger bar pivotally connected at an intermediate point along its length within the support rail, said trigger bar having an upper end portion projecting above the rail and connected to the fire control cable and having .a lower end portion projecting downwardly into the rail and engaged in the catch opening of the pusher bar, whereby the trigger bar normally holds the fire control trolley in said retracted position and whereby the force exerted by the retriever cable in door closing direction reacts through the trigger bar and is resisted by the fire control cable, said trigger bar adapted to swing to a release position upon parting of the fire control cable, whereby the pusher bar of the fire control trolley engages one of said door support trolleys to shift the door in closing direction upon release of the fire control trolley in response to a predetermined temperature above normal acting upon the fire control cable.

4. A heat responsive fire door control apparatus adapted to close a pair of doors with reference to a door opening in a fire wall comprising:

a door support rail mounted in a generally horizontal plane above the door opening and having opposite outer end portions extending transversely beyond opposite sides of the door opening;

said support rail having open inner end portions spaced apart from one another above the door opening;

said support rail being generally of inverted U-shape in cross section and having inturned flanges projecting toward one another along the lower edge of the rail and delineating a longitudinal slot;

a plurality of spaced door support trolleys translatably confined within said support rail and having pairs of rollers tracked upon the inturned flanges of the rail, said door support trolleys having hanger means projecting downwardly through said slot and connected to said doors for suspending the doors from the rail for movement to open or closed positions relative to the door opening;

a pair of shiftable fire control trolleys translatably confined within said support rail and having pairs of rollers tracked upon the inturned flanges of the rail, said fire control trolleys normally residing in retracted positions at the opposite transversely extended end portions of the support rail;

said fire control trolleys normally disconnected from said doors, adapting the doors to be shifted manually relative to one another to open or closed positions with reference to the door opening;

a pair of spring-loaded retriever reel assemblies mounted relative to the door support rail at a midpoint along the length of the rail;

each of said retriever reels including a housing, said housings being disposed adjacent the open inner ends of the door support rail at the mid-point thereof;

each retriever reel assembly having a retriever cable extending outwardly and connected under tension to a respective fire control trolley, thereby normally urging the fire control trolleys toward one another in door closing direction;

said retriever cables passing from said housings and outwardly in opposite directions through the door support rail, whereby the housings and door support rail enclose the retriever cables to protect the same from damage;

a respective trigger bar pivotally connected to said rail at opposite end portions thereof, said trigger bars each having an upper portion projecting upwardly above the support rail and having a lower portion projecting downwardly into the rail and in latching engagement with a respective fire control trolley, said trigger bars normally latching the fire control trolleys in the retracted position counter to the tension exerted by the retriever cables;

a heat responsive fire control cable having opposite ends connected to the upper end portion of each trigger bar and normally holding said trigger bars in said latching position;

at least one fusible link interposed in the fire control cable, said fusible link adapted to melt at a predetermined temperature above normal, thereby to release both of said trigger bars;

said fire control cable, upon melting of said link, releasing the trigger bars and unlatching the fire control trolleys, adapting the retriever cables to shift the fire control trolleys toward one another in door closing direction;

said fire control trolleys, upon release thereof, adapted to engage one of the door support trolleys of each door and to shift said doors toward one another to closed position by operation of the retriever reel assemblies. 5 References Cited UNITED STATES PATENTS 2,876,504 3/1959 Bennett et a1. 49--409 3,189,142 6/1965 Carlson 49 7 555,652 3/1896 Miller 49-7 814,192 3/1903 Dentler 49 3 FOREIGN PATENTS 471,941 9/1937 Great Britain.

15 DAVID J. WILLIAMOWSKY, Primary Examiner.

J. KARL BELL, Assistant Examiner. 

